Search for Light Dark Matter–Electron Scattering in the PandaX-II Experiment

We report constraints on light dark matter through its interactions with shell electrons in the PandaX-II liquid xenon detector a total 46.9 tonne$\cdot$day exposure. To effectively search for these very low energy electron recoils, ionization-only signals are selected from data. 1821 candidates identified within ionization signal range between 50 to 75 photoelectrons, corresponding mean electronic recoil 0.08 0.15 keV. The 90% C.L. exclusion limit scattering cross section and is calculated based Poisson statistics. Under assumption of point interaction, we provide world's most stringent mass 15 30 $\rm MeV/c^2$, $2.5\times10^{-37}$ $3.1\times10^{-38}$ cm$^2$.